1. Field of the Invention
This invention relates to a cleaning member for removing a residual parting agent attached to a photosensitive member, a transfer carrier member, a member disposed along a transport path, a transfer member after fixation provided in an electrophotographic apparatus and also relates to an electrophotographic apparatus using the cleaning member.
2. Description of the Related Art
Various kinds of electrophotographic apparatuses in which a toner image on an image carrier member such as a photosensitive member or an insulating member is transferred to a transfer member by making the transfer member face the image carrier member one or a number of times to obtain a monochromatic or color image, e.g., electrophotographic copying machines and printers, have been proposed and put on the market. A cleaning member for such electrophotographic apparatuses, i.e., for removing residual silicone oil attached to an image carrier, transfer member carrier member, such as a transfer drum, a member disposed along a transport path, a transfer member after fixation is formed of, for example, a cloth-like member impregnated with a dispersion liquid of a polishing material, which is a cleaning member for an electrophotographic member disclosed in Japanese Patent Laid-Open Publication No.55-166672.
FIG. 2 shows an example of a color electrophotographic copying machine for forming a full color image. In the color electrophotographic copying machine, as illustrated, an electrophotographic photosensitive member in the form of a drum provided as an image carrier, i.e., a photosensitive drum 1 is supported so as to be rotatable in the direction of the arrow, and a corona charging unit 2, an exposure optical system 3, a development unit 4, a transfer unit 5 and a cleaner 6 are disposed around the photosensitive drum 1.
The optical system 3 has an original scanning unit 3a and a color decomposition filter 3b. By the optical system 3, the photosensitive drum 1 uniformly charged by the charging unit 2 is irradiated with an image light of each of the color-decomposed images to form a latent image. The development unit 4 of a rotary type has four development devices, i.e., a yellow development device 4Y, a magenta development device 4M, a cyan development device 4C and a black development device 4B disposed about a center axis 4b. Each development device is rotated to a predetermined position such as to face the photosensitive drum 1 to form a toner image on the photosensitive drum 1 by developing the corresponding latent image on the photosensitive drum 1.
The toner image formed on the photosensitive drum 1 is transferred to a transfer member which is supplied from a transfer member cassette 7 through a transport system and the transfer unit 5 and set in a position such as to face the photosensitive drum 1. The transfer unit 5 has a cylinder 5a, a transfer charging device 5b, a transfer member gripper 5c for holding and transporting a transfer member, an inner charging device 5d, and an outer charging device 5e. A transfer member carrying sheet 5f formed of a dielectric material is stretched cylindrically on a circumferential surface opening region of the cylinder 5a.
As the above-described drum-like transfer unit (transfer drum) 5 is rotated, the toner image on the photosensitive drum 1 is transferred to a transfer member carried by the transfer member carrying sheet 5f by the transfer member charging device 5b. The transfer member is attracted to the transfer member carrying sheet 5f. Residual toner on the photosensitive drum 1 is removed by the cleaner 6 and is successively used for the next cycle of the image formation process.
In this manner, the desired number of color images are transferred to the transfer member transported while being attracted to the transfer member carrying sheet 5f. This color image formation method is well known to those skilled in the art and will not be described in more detail.
When transfer of four-color toner images is completed, the transfer member is separated from the transfer drum 5, processed by a hot roller fixation device 9, and discharged onto a tray 10.
In the color electrophotographic copying machine described above, the transfer carrier member for holding a transfer member, i.e., transfer member carrying sheet 5f formed of a dielectric material, is stretched over a circumferential surface opening of the transfer drum 5. In the vicinity of the circumferential surface of the transfer drum 5, however, the other units, i.e., the photosensitive drum 1, the development unit 4 and the cleaner 6, which carry or contain a developer (toner) are disposed. It is possible that unnecessary toner scattered from these units will attach to and contaminate the transfer member carrying sheet on the transfer drum 5. Also, when the transfer member is separated from the transfer drum 5 before toner image is fixed after the transfer of the toner image to the transfer member, toner on the transfer member attaches to the transfer member carrying sheet 5f and seriously contaminates the same if transfer member jamming occurs (if the transfer member clogs in the mechanism).
Therefore, a transfer member carrying sheet cleaner, i.e., a cleaning means 11 is provided on the transfer unit 5 for the purpose of removing toner attached to the transfer sheet carrying sheet 5f. Ordinarily, cleaning of the transfer member carrying sheet 5f is performed during pre-rotation of the transfer drum 5 effected before transfer. However, it is performed any time after transfer member jamming or the like as described above.
The transfer member carrying sheet cleaner 11 is constructed in such a manner that, as shown in FIG. 2, a fur brush cleaner 11a is disposed outside the transfer member carrying sheet 5f cylindrically stretched over the peripheral surface opening of the cylinder 5a to serve as a means for supporting the transfer member carrying sheet, while a backup brush 11b is disposed inside the transfer member carrying sheet 5f.
The above-described conventional copying machine, however, entails a problem in that a parting agent such as a silicone oil attached to a transfer paper sheet after fixation attaches to a feed roller, a sheet transport means, the transfer drum and the photosensitive drum to obstruct image formation process, if the transfer sheet on which an image has been fixed is fed again to complete two-surface image formation. In particular, if silicone oil is attached to the photosensitive drum, a phenomenon called oil fog occurs. The mechanism causing this problem will be described with reference to FIGS. 3 to 5.
FIG. 3 shows a state of transfer of a part of silicone oil existing on fixed toner to the transfer drum.
FIG. 4 shows a state of transfer of transferred silicone oil existing on the transfer drum to the photosensitive drum through a nip during post-rotation.
FIG. 5 shows a state in which transferred silicone oil transferred to the photosensitive drum adhesively collects toner existing around the photosensitive drum and is transferred at the time of the next transfer to cause fogging.
For prevention of such a phenomenon, it is necessary to rapidly remove transferred silicone oil. However, the above-described cloth-like member impregnated with a dispersion liquid of a polishing material or a cloth-like member simply formed of a nonwoven fabric is incapable of removing transferred oil and only spreads the oil as a film on the surface to be cleaned. Also, silicone oil cannot be removed by the fur brush.